1. Field of the Invention
The present invention relates to a slurry composition for a chemical mechanical polishing process and a method of manufacturing a semiconductor device using the same, and, more particularly, to a slurry for a chemical mechanical polishing (hereinafter referred to as “CMP”) process that results in a high selectivity ratio to polysilicon and to a method of planarizing the surface of a semiconductor device using the same.
2. Description of the Related Art
The high performance and high integration requirements of modern semiconductor devices demand a multilayer interconnection structure. This multilayer interconnection structure is typically made by performing the sequential steps of film forming/layer deposition followed by an etch process of conductive layers and insulating layers, and repeating these steps several times. Predetermined patterns required for each layer are formed, and then a surface planarization step is performed so that a lithographic process may be easily performed before another pattern is formed.
This planarization step is classified into local planarization and global planarization. The ultimate object of planarization technology is to realize global planarization. Techniques for this global planarization typically include the steps of forming a coating of resin, such as polyimide, followed by an etch-back step, a reflow, and a CMP for the metallic and insulating layers.
A wafer on which a planarization process will be performed is mounted on a rotatory plate, and the surface of the wafer is made to contact a polishing pad. After this, CMP is carried out by rotating the rotatory plate and the polishing pad while providing a supply of slurry between the wafer surface and the polishing pad. In other words, a CMP process is a combination of a chemical action of a slurry, comprising a chemical solution and abrasive grains, and the mechanical action of a polisher. The slurry is supplied between the wafer surface and the polishing pad, and mechanical friction is generated due to the abrasive grains in the slurry and the surface of the pad. As a result of the mechanical effects, the wafer surface is polished. At the same time, part of the wafer surface is removed by the chemical reaction of the chemical components in the slurry with at least portions of the wafer surface.
In general, various kinds of CMP slurries are used depending on the characteristics of the wafer surface materials to be removed. In particular, in a case where a polysilicon layer and a silicon oxide layer are being polished by a CMP method employing a silica-based slurry using silica (SiO2) as an abrasive grain, over a given period about twice as much of the polysilicon layer will be removed than the amount of the silicon oxide layer removed. Thus, it can be said that the selectivity ratio of the polysilicon layer to the silicon oxide layer for this CMP process is about 0.5:1. It is therefore difficult or impossible to use a polysilicon layer as a polishing stopping layer when a CMP process is carried out in a specific step of a semiconductor device manufacturing process when using a conventional silica-based slurry. However, for some applications it may be inevitable to carry out such a CMP process despite the problem of the selectivity ratio between a polysilicon layer and a silicon oxide layer in a manufacturing process of a semiconductor device. Alternatively, it may be desirable to use a polysilicon layer as a polishing stopping layer in several steps, not only in a single specific step. Accordingly, it would be desirable to develop a new slurry composition which can be useful in carrying out these types of CMP processes.